Monty Python legend Terry Gilliam has joined thousands of victorious campaigners today in celebrating historic Athlone House being saved from demolition, describing it as “fantastic news”.

The Hollywood director has long been a passionate defender of the Victorian former hospital on the edge of Hampstead Heath, supporting the latest three-year campaign to protect it.

Last year, developers Athlone House Limited appealed to the Planning Inspectorate to knock down the former RAF intelligence base and replace it with an opulent neo-classical eight-bedroom family home, complete with basement car park, swimming pool and ballroom.

But today, planning inspector Colin Ball dismissed the appeal in a landmark decision for the 5,000 campaigners who fought to protect the mansion.

Mr Gilliam said: “It is fantastic news that the planning inspector has dismissed the appeal to demolish this wonderful historic house on the fringes of Hampstead Heath.

“I was appalled that the owner tried to wriggle out of his legal obligation to restore the building which is why I became involved.

“My congratulations to the Highgate Society and the Heath and Hampstead Society who have fought so hard to save Athlone House!”

The owners were obligated to restore the Highgate mansion under an historic planning agreement when planning permission for luxury flats in the grounds of Athlone House was granted back in 2004.

But Camden Council has been unable to enforce the agreement ever since because of a legal loophole.

In his appeal decision, Mr Ball described the proposals as “inappropriate” and potentially “harmful” to Hampstead Heath.

A spokesman for Athlone House Limited said: “This is a very disappointing decision. We will be looking carefully at the inspector’s decision before deciding the next steps.”